Autoleveller draw frame having process feed back control system

ABSTRACT

An apparatus for controlling a fiber processing plant including a series of processing stages in order to supply fibrous material as a product with predetermined qualities, whereby the qualities of the product can be influenced by suitable, selectively adjustable treatment of fibrous material during its passage through the plant and whereby in at least one of the intermediate stages of the plant an ascertainable quality of the product of this stage is determined. In this intermediate stage a signal is obtained which is equivalent to the ascertainable quality and which is used for controlling the previous stages.

This application is a division of application Ser. No. 07/855,015, filedon Apr. 27, 1992, which is a continuation of international applicationNo. PCT/CH91/00140, filed on Jun. 25, 1991.

The invention relates to a method for gaining information and generatingsignals which is particularly suitable for use in a process controlsystem for a spinning mill. The information or the signals thus gainedmay be used for controlling or regulating purposes or for operationalsupport.

DESCRIPTION OF BACKGROUND AND RELEVANT INFORMATION

A present conventional spinning plant uses fibrous material in the formof bales as the feed material and converts it into yarn over a series ofvarious processing stages. The yarn must fulfill predefined qualityspecifications. The ability to control the conversion automatically isone object of the invention, as will be discussed below. For variousreasons this is a very difficult task, of which only some categories ofsuch shall be mentioned below:

There are the various requirements that the product of the spinning mill(yarn) has to fulfill by its further processing to a final product (e.g.a product made from woven or knitted fabric).

There is the number of processing stages that have a decisive influenceon the conversion of the fibrous material to yarn.

There are the various technological factors that have an impact on eachprocessing stage.

It has been proposed to divide the spinning line into "areas" that areeach attributed to an own process control computer, whereby variousdivisions have been proposed by various persons (see also DE-A-39 24779, Maschinenfabrik Rieter AG, and DE-A-39 06 508, Murata Kikai K. K.).

It has also been proposed to combine by way of control the firstprocessing stages of the spinning line (the blow room and the cardingroom), i.e. DE-A-32 37 864, EP-A-0 303 023 and U.S. Pat. No. 4 876 769.Proposals have been submitted which allow controlling both thecomposition of the material to be processed as well as the processing ofsaid material in the first stages of the spinning line, i.e. EP-A-0 362538; EP-A-0 402 940, EP-A-0 399 315 and EP 90 810454.0.

It is still common practice to monitor the evenness of the product ofthe card (card silver) and to control the card in such a manner thateither the best possible or predetermined evenness of the card sliver isachieved (see, for example, U.S. Pat. No. 4,271,565).

Data transmission systems are also presently used for connecting thespinning line or its controls with an overlaid process control system.For further details refer to the Swiss patent application No. 189/91 ofJan. 23, 1991 (lectures of Messrs. Dr. U. Meyer and H. Howald on theoccasion of the VDI annual meeting in Aachen on Jan. 30 and 31, 1991).The first plans for realizing such a process control system in theSpinning mill rather aimed at an essential improvement in operationalsupport than "fully automatic operation"; see PCT patent application No.PCT/CH 91/0097 of Apr. 23, 1991.

The efforts of various firms which are active in this field oftechnology mainly aim at connecting the above-mentioned first stages andthe last stages (end spinning and roving yarn stages) of the spinningline and the subsequent bobbin winding machine (for ring-spun yarn) withthe process control system; see. EP-A 0 365 901. However, between thesefirst and last stages there are still some other processing stages thatfulfill important tasks in processing the material and that are able tosupply important information to the process control system.

SUMMARY OF THE INVENTION

It is the object of the present invention to reduce the complexity ofthe overall problem of fully automating a spinning line by extractingidentifiable parts of problems.

The invention provides a method for controlling a fibre processing plantcomprising a series of processing stages in order to supply fibrousmaterial as a product with predetermined qualities, whereby thequalities of said product can be influenced by suitable, selectivelyadjustable treatment of fibrous material during its passage through theplant and whereby in at least one of the intermediate stages of saidplant an ascertainable quality of said product of this stage isdetermined, thus allowing the respective quality of the product to bedecisively influenced or determined.

A particular feature of the method is that in the mentioned intermediatestage a signal is obtained which constitutes a measure for theascertainable quality of the intermediate product mentioned above.

This signal can be used for controlling at least one processing stagewhich the fibre has to pass before reaching the mentioned intermediatestage and which can have an influence on the mentioned ascertainablequality. The signal can, however, also be displayed in a suitable mannerand thus used for operational support i.e., assistance to the operatingstaff.

In a particularly preferable example of this method the intermediatestage is a combing plant and the ascertainable quality is the proportionof short fibres in the material to be processed. The previous stages arethe blow room, the opening room and the carding room of the plant. Thesignal obtained in the carding room can be used for controlling a mixingprocess and/or for controlling the intensity of the opening and cleaningof the fibrous material. If the idle time of the intermediate processingdoes not allow a control based on the signal gained in the carding room,the signal can be suitably processed for operational support, whereby,for example, an alarm is provided with respect to the behaviour of theprevious stages or with respect to the supplied material.

The invention also relates to a fibre processing plant which includes ameans for obtained the mentioned signal and a controlling means for theprevious stage which can influence the ascertainable quality. This mayalso include automatic intervention on the part of the control unit. Theplant may, however, also comprise a display means which serves as adecision support tool for an intervention to be carried out by theoperating personnel.

The condition displayed by the mentioned signal is preferably comparedwith a predefined desired condition (e.g. in a computer) in order toestablish any deviations from the desired condition. When such adeviation from the desired condition is detected, a control process ispreferably carried out at first in order to determine whether thisdeviation was not caused by the intermediate stage (e.g. the cardingroom) itself. In the latter case no control signal is sent to thecontrolling means for the previous stages. The error condition of thementioned intermediate stage is displayed or removed by suitablemeasures. Only when an error condition of the intermediate stage is nolonger detected should a control signal be sent to the previous stage orto its control unit.

The above-mentioned comments on the invention mainly deal with thecomposition of the material, in particular the proportion of shortfibres. As is explained below by reference to the Figures, theproportion of short fibres of the yarn is determined by the combingroom. Further features of intermediate products of a spinning mill areof importance for the final results.

An important quality feature of the said fibre product is its so-called"evenness" which can be defined by the fibre mass per length unit of theproduct.

In a well-managed spinning plant of the present conventional type theevenness of the final product (the yarn) is substantially determined bythe end spinning process (flyer and ring spinning or rotor spinning orany other new spinning process). The preparatory stages contribute verylittle to the final result (concerning unevenness).

However, one cannot simply draw the conclusion that the control ofevenness in the preparatory stages can be neglected. Serious mistakescan also occur in the preparatory stage of a well-organized spinningplant and can have a decisive influence on the final result. Inaddition, the competitiveness of a spinning plant depends on very smalldifferences in their product to those in the products of theircompetitors. Therefore it is necessary to make even the smallestpossible contributions for reducing unevenness. Note must be taken ofthe fact that in the end spinning process (at least in presentlyavailable spinning machines) it is not possible to rectify flaws in theevenness of the fed material. Efforts in the field of end spinningmethods aim at limiting the unevenness caused by the end spinningprocess itself.

For the reasons mentioned above, measures are mostly taken in thepreparatory stages either to improve the evenness of the intermediateproduct of each processing stage or at least to keep it under control.As the last measure before the end spinning the fibre structures areoften subjected to a draft in an autoleveller draw frame in order toimprove the evenness of the structure before it is fed to the endspinning process.

The above-mentioned statements make it quite clear that an autolevellerdraw frame is not able to determine the evenness of the final product ofthe whole spinning line (the yarn), because this result is determined bythe end spinning process itself. However, such an autoleveller drawframe is able to determine the contribution of the preparatory stages tothe unevenness of the final product and it is the task of such a drawframe to reduce this contribution to a minimum. If the autoleveller drawframe manages to fulfill this task, its intermediate product and theproducts of the following processing stages do not contain anyinformation which allows drawing conclusions on the performance of theprevious processing stages.

In accordance with a second aspect of the invention, at least the lastautoleveller draw frame or the last evenness control unit before thespinning is defined as a master control unit which is responsible forthe evenness of the intermediate products of the processing stages thatare previous to this respective one and that supply it with material.Every autoleveller draw frame or evenness control unit can be arrangedas such a master control unit.

Principally, every spinning mill preparatory machine for formingslivers, nonwoven fleeces or flocks could be provided with an ownautoleveller draw frame or an evenness control unit and an evaluationmeans which are able to check the quality of the supplied material withrespect to evenness by means of the control work carried out by the drawframe or the control means. A spinning line with such machines iseffectively divided into sections, each ending with an autoleveller drawframe or autolevelling means, whereby said draw frame or autolevellingmeans serves, with respect to the evenness, as master control unit forthe section allocated to it.

If it is not possible or desired that each preparatory machine isprovided with an own autoleveller draw frame or its own autolevellingmeans, at least one autoleveller draw frame or autolevelling means isprovided before the end spinning process, said frame or means serving,with respect to the evenness, as the master control unit for the sectionof the processing line that feeds said frame or means with feedmaterial.

The invention, with respect to this aspect, may be applied both withregard to longwave as well as shortwave deviations in evenness, wherebydifferent autolevelling means can be provided for varying types ofdeviations.

The signals obtained by this system can be combined with a material flowtracing system in order to allow or enable the diagnosing ofmalfunctions. A material flow tracing system that is suitable for thispurpose is described in the DE-A-40 24 307 of Jul. 31, 1990 and incorresponding U.S. application Ser. No. 07/852,153, whereby thisinvention is not limited to the use in such a combination.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now outlined in greater detail in examples by referenceto the drawings, in which:

FIG. 1 shows a schematic outline of a spinning plant for the processingof fibre bales up to ,the spinning of ring-spun yarn;

FIG. 2 shows a diagram for displaying the same spinning mill, wherebythe various processing stages are shown for reasons of simplificationwithout breaking down each stage into individual machines;

FIG. 3 shows a staple diagram of a typical fibrous material forprocessing in a so-called short fibre spinning mill;

FIG. 4 shows a schematical layout of a bale opener;

FIG. 5 shows a schematical side view of a fibre opening or cleaningmachine;

FIG. 6 shows a schematic view of a process control system in accordancewith our application DE-39 24 779 of Jun. 26, 1989, and U.S. Pat. No.5,161,111;

FIG. 7 shows a schematic side view of a combing machine in accordancewith our German Patent DD 286 376 and U.S. Pat. No. 5,230,125;

FIG. 8 shows a schematic view of a single combing head of the machine inaccordance with FIG. 7;

FIGS. 9A and 9B show two time diagrams for explaining variousmeasurement principles;

FIG. 10 shows a diagram for explaining various measuring arrangementsfor gaining a suitable signal in the combing room, and

FIG. 11 shows a schematic view of preferred draw frame drive for anautoleveller draw frame in accordance with EP-A-0 411 379 and U.S. Pat.No. 5,248,925.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description at first deals with the spinning line in itsentirety and the process control system, then the composition of thematerial and the combing room, and finally the evenness and theautoleveller draw frame.

The Spinning Line

The spinning mill as shown in FIG. 1 comprises a bale opener 120, acoarse cleaning machine 122, a mixing machine 124, two fine cleaningmachines 126, twelve carding machines 128, two draw frames 130 (firstdrawing passage), two combing preparatory machines 132, ten combingmachines 136, four draw frames 138 (second drawing passage), five flyers140 and forty ring spinning machines 142. This is a conventionalarrangement for producing so-called combed ring-spun yarn. The ringspinning process can be replaced by a newer spinning method (e.g., therotor spinning process), whereby the flyers can then be left out. As,however, this invention deals with preparatory stages before the endspinning (plus any optional end spinning preparations in a flyer stage),the statement in connection with conventional ring spinning issufficient for using the invention with new spinning methods. Thecombing room may be of importance in new spinning methods, particularlyif higher qualities are required.

The spinning mill of FIG. 1 is again schematically shown in FIG. 2,whereby in the latter case the machines are combined to form so-called"processing stages". Accordingly, the bale opener 120 and the coarsecleaning machine 122, the mixing machine 124 and the fine cleaningmachine 126 jointly form a so-called blow room 42 which supplies thecarding room 44 with substantially opened and cleaned fibrous material.Within the blow room the fibrous material is conveyed in a pneumaticconveying system (air stream) from machine to machine, whereby thesystem ends in a carding machine. The carding machines 128 each supply asliver as intermediate product which is deposited in a suitablecontainer (a so-called "can") and conveyed further on.

The first drawing passage (through draw frames 130) and the seconddrawing passage (through draw frames 138) each form a processing stage46 and 52 (FIG. 2), respectively. In between, the combing preparatorymachines 132 form a processing stage 48 (FIG. 2) and the combingmachines 136 form a processing stage 50 (FIG. 2). Finally, the flyers140 form a spinning preparatory stage 54 (FIG. 2) and the ring spinningmachines 142 form an end spinning stage 56 (FIG. 2). This applicationwill not explain the latter two processing stages in greater detail.

The Process Control System

The process control system is no essential feature of this invention.The invention also offers advantages in the event that the obtainedsignals or information is used directly (without directing them througha process control system). The preferred embodiment, however, providesthat the invention is used in combination with a process control system.Examples of such systems are briefly explained below.

In our German patent application No. 39 24 779 of Jun. 26, 1989 and U.S.Pat. No. 5,161,111 a process control system is disclosed according towhich a spinning mill is organized in "areas" and by which signals fromone area can be used to control previous areas. An example for such aplant is schematically shown in FIG. 6, whereby the plant comprisesthree areas B1, B2 and B3 and whereby each area is allocated its ownprocess control computer R1, R2, R3. Each computer R1, R2, R3 isconnected for exchanging signals with the machines or groups of machinesof its own area (schematically shown in FIG. 6 by the lines 84) and thecomputers are connected with one another for the exchange of signals,too (schematically shown in FIG. 6 by the connections 86). It is quiteobvious to the man skilled in the art that the view shown in FIG. 6 ispurely schematical. Naturally, it is also possible that there is onlyone single process control computer which is connected with all areas ofthe spinning mill and which carries out the exchange of signals betweensaid areas. The illustrated embodiment with one process control computerR per area B has proved to be a sensible arrangement, which will be usedfor the explanations below.

Area B1 comprises the blow room 42 and the carding room 44 (FIG. 2).

Area B2 comprises both the two draw passages 46, 52 (FIG. 2) as well asthe combing preparatory stage 48 and the combing room 50.

Area B3 comprises the flyers 54 and the end spinning stage 56 (FIG. 2).

With respect to the preferred embodiment of this invention, areas B1 andB2 are of importance, whereby signals that are obtained in the combingroom (area B2) are used for controlling the machines in the area B1 viacomputers R2 and R1. Details on how the respective signals are obtainedare outlined below with reference to FIGS. 7, 8 and 9.

A process control system in the spinning mill is preferably programmedand designed or arranged for tracing the flow of the material. Theimportance of this task and proposals for a solution are provided in UweBehren's article "Computer-supported Transport Systems in TextileManufacture" (Melliand Textile Reports, 7/1985, p. 499). The applicant'spreferred solution, however, is contained in U.S. application Ser. No.07/852,153 and in the German Patent Application No. 40 24 307.9 of Jul.31, 1990 and the corresponding PCT application No PCT/CH91/00151, whichwill be filed until Jul. 31, 1991.

An additional important task of a process control system is operationalsupport (i.e., assistance to the operating staff). Present conventionalspinning mills comprise a number of devices, programs and auxiliarymeans which help the operating staff to carry out the complex tasksquickly and efficiently. In the "fully automated" spinning mill of thenext generation it will be necessary to principally integrate theoperator supporting means into the process control system. Such asolution has already been proposed by the applicant in U.S. applicationSer. No. 07/778,813 and in the PCT application PCT/CH 91/00097.

The "architecture" (the arrangement) of the process control system isalso of importance because of the complexity of the spinning line,particularly with respect to information transmission. Proposedsolutions in U.S. application Ser. No. 07/927,307 and in this respectare contained in the Swiss Patent applications No. 189/91 of Jan. 23,1991 and No. 1025/91 of Apr. 5, 1991.

The Composition of the Material

The final result of the schematically displayed spinning process isinfluenced by a large number of factors, which will not be explainedhere in greater detail. One important factor is the raw material to beprocessed, which can be regarded as a group of individual, ascertainablefibre qualities (e.g. fibre fineness, type and strength of fibre, etc.).

One essential quality for the final result of the spinning process isthe fibre length, which can only be ascertained and displayed properlyby statistical methods in relationship to the number of fibres that haveto be processed. The fibre length quality of a certain raw material istherefore represented by a so-called staple diagram (FIG. 3) (see alsopage 24 of the manual "Textile Fibres: Testing and Quality Control";Author: S. L. Anderson in Manual of Textile Technology, Quality Controland Assessment; Publisher: The Textile Institute). The proportion(percentage rate) of fibres in a given length range can be evaluated forthe respective raw material by this diagram. The importance of the fibrelength for the spinning is known from the manual "Technology of ShortStaple Spinning", author: W. Klein in Manual of Textile Technology,Short Staple Spinning Series, (Vol. 1), publisher: The TextileInstitute.

When processing natural fibres (in particular cotton fibres) it is notpossible to "order" raw material with a predefined staple diagram. Onthe contrary, it is necessary to produce the desired diagram by Suitablyprocessing fibres from various sources ("origins"). In particular, threeprocessing stages have a decisive influence on the material to be spun,which are:

the blow room

the carding room

the combing room

The effects of the blow room and the carding room are briefly describedbelow, because these stages are only indirectly affected by the presentinvention:

The Blow Room

In principle, there are two ways to influence the staple diagram of araw material in the blow room or carding room, namely:

by supplying fibres of varying lengths (origins), and

by the intensity of the fibre processing, whereby a higher intensityautomatically leads to a higher rate of damage (shortening) to thefibres.

Examples of these two options are schematically outlined in FIGS. 4 and5.

FIG. 4 schematically shows a bale opener of the present conventionaltype with a tower 60 which can move back and forth along a duct 62. Thetower 60 comprises an extension arm 64 with a bale opener unit (notshown). The fibre bales are placed the application form of bale groups66, 68, 70, 72 next to the duct 62. During the reciprocating movement oftower 60 with the: extension arm 64 disposed above a given bale group(in FIG. 4 above bale group 68), the opening unit removes fibre flocksfrom the surface of the bale and feeds them to duct 62 by way of apneumatic conveyor system (not shown). The conveyor system mentionedabove then supplies said fibre flocks to the other machines of the blowroom and, finally, to the carding room.

If the bale groups are arranged according to their origin (so that, forexample, fibres of a first origin are placed in bale group 68 and fibresof a second origin are placed in the bale group 66), the staple diagramof the material to be spun can be influenced in such a way that the baleopener conveys a larger amount of fibres for processing from, forexample, bale group 68 than from bale group 66. In such a way theso-called fibre mixture can be influenced very roughly.

A further development of the conventional system has been shown in U.S.Pat. No. 5,025,533 and U.S. patent application Ser. No. 07/536,205, aswell as in the European patent applications EP-A-0 362 538 and EP-A-0402 940, wherein the fibre mixture is made as desired. The respectiveprocess requires a control unit which has to be arranged in connectionwith the stages blow room/carding room.

FIG. 5 schematically shows a rotatable drum 74 of a cleaning machine,e.g. a fine cleaning machine 126 (FIG. 1). Said drum 74 cooperates, forexample, with a grate consisting of individually adjustable grate rods76 (only one grate rod 76 is shown in FIG. 5). Each grate rod 76 isrotatable about an axle 78 and comprises a work head 80 at its endadjacent to drum 74. By displacing grate rod 76 about the axle 78 it ispossible to change the position of the work head in respect to drum 74.This measure has an influence on the intensity of the processing duringthe cleaning of the material. A more intense processing means a higherdegree of cleaning. On the other hand, it also means more damage to(shortening of) the fibrous material to be processed. The setting of therods 76 can also be carried out manually. It can also be madeautomatically by means of servomotors 82. Other places where it ispossible to carry out more intensive fibre processing at the expense ofhigher damage to the fibres (shortening) are the bale opening room andthe carding room. A method which makes direct use of this effect isshown in U.S. patent application Ser. Nos. 07/785,237 and 07/905,531, aswell as in the European patent applications EP-A-0 399 315 and EP-A-0409 772.

The Combing Room

The last stage that has an influence on the staple diagram of the rawmaterial to be spun and that determines said diagram for the endspinning process is the combing room. The function of said stage isfirst outlined below. It is assumed that present, conventional combingmachines are used, so that it is unnecessary to explain in detail thedesign (arrangement) and operation of a combing machine. Such details,for example, are known from the book "Drawing, Combing and Roving",author: Zoltan S. Szalocki, publishers: The Institute of TextileTechnology or from the manual "A Practical Guide to Combing and Roving",authors W. Klein in Manual of Textile Technology, Short Staple SpinningSeries, (Vol. 3), publisher: The Textile Institute. A modern combingplant is described in the article "The Combing Room as the DecisiveProfitability Factor in Short-Staple Spinning" by Dr. G. Mondini inMelliand Textile Reports, 5/2990, p. 330ff.

The above sources clearly indicate that the essential function of acombing machine consists of filtering out fibres of an ascertainableminimal length from the process as wastage. This effect can be explainedvery clearly in connection with the diagram of FIG. 3. It is assumedthat the blow room 42 or the carding room 44 supplies to the combingroom 52 a raw material with the fibre characteristics C in accordancewith the staple diagram of FIG. 3. The combing machines 136 (FIG. 1) ofthis combing room are set in such a way that they filter out all fibresas wastage that are shorter than X mm (it serves as a "separating point"with respect to the short fibres). Under these assumed prerequisites,the filtered short fibres constitute a proportion of Y% of the feedmaterial supplied by the preparatory stage 50 (FIG. 2). The situation asshown in FIG. 3 constitutes the scheduled condition. Deviations fromthis scheduled condition can be determined by the proportion of shortfibres that are filtered out in the combing room. This allows usingmeans for controlling the blow room and/or the carding room. Note mustalso be taken of the fact that the combing machine not only filters outshort fibres, but also filters out neps and soil. However, these amountsof wastage are negligable in comparison to the amounts of short fibresthat are filtered out.

FIG. 7 is a copy of FIG. 1 of U.S. Pat. No. 5,230,125 and our earlierSwiss Patent application No. 4754/88 (DD 286 376) and shows a schematicside view of a combing machine with a controlled drafting device. Onlythe basic structure of the combing machine (without considering the drawframe control unit) will be explained hereinunder at first.

FIG. 7 shows a combing machine 1 with, for example, eight combing heads2, of which only four are shown in the drawing. A single combing head 2is schematically shown in a larger scale in FIG. 8 (with a view in thelongitudinal direction of the machine). On the carrier rollers 110 (FIG.8) in each combing head 2 there is a lap roll 3 whose lap 4 is suppliedto the combing apparatus 5 through a supply means 112 (FIG. 8). As isgenerally known, the combing apparatus 5 may consist of a nippers unit114 (FIG. 8), a circular comb attached under said unit and, with respectto the conveying direction, a top comb 118 arranged behind said nippersunit. Behind said top comb are arranged detaching rollers 119.

The combed fibre fleece supplied by the detaching rollers 119 reaches adraw-off funnel (not shown in greater detail) over a delivery table 6(FIG. 7). In the draw-off funnel the fibre fleece is combined to form asliver or a combed sliver. This process is supported by a pair ofdraw-off rollers 7 that are arranged behind the respective draw-offfunnel. Said rollers supply the combed sliver to an outlet table 8. Inorder to continue the conveyance of the slivers 10 next to each other onthe outlet table 8, sliver guiding means 9 are provided which aredisplaced from one another in the horizontal direction. The slivers 10guided parallel towards each other reach a draw frame 11, whereby ameasurement unit 12 is provided at the entrance of the draw frame 11.Said measurement unit scans the thickness of the incoming slivers. Themeasurement unit 12 can be arranged in a number of ways, for exampleoptically or mechanically.

After passing the measurement unit 12 the slivers reach a central pairof rollers 15 between the feed rollers 13 of a preliminary draft zone14. Said central pair of rollers 15 simultaneously form the feed rollersfor a subsequent main draft zone 16. The drawn slivers 10 reach aschematically shown sliver funnel 18 through the delivery rollers 17 atthe outlet from the main draft zone 16. There they are combined to acombed sliver 19 by means of the draw-off rollers 20. A pressure bar 21is attached in the preliminary draft zone for guiding the slivers. Thispressure bar 21 could also be arranged in the main draft zone.

The combed sliver 19 supplied by the draw-off rollers 20 reaches aconveyor belt 22 and is conveyed to a can frame 23. The combed sliver 19is deposited in a can 26 by means of calender rollers 24 and the funnelwheel 25.

The shorter fibres are picked up by the wire setting 117 (FIG. 8) of thecircular combing and removed from the circular comb 116 by means of acomb cleaning means KR. The cleaning means conveys these separated shortfibres to a suction duct 121. Said duct 121 passes all eight combingheads 5 and conveys the wastage from said heads to a collectingcontainer SB. The separated material can, for example, be used in arecycling process again. However, this process is not of importance forthe present invention and shall therefore not be described hereinunder.

In accordance with FIG. 3 it is desired to obtain a signal which isequivalent to the proportion of short fibres of the feed material forthe combing room. This is achieved by a suitable arrangement ofmeasuring sensors. In principle it would be possible to individuallymeasure the proportion of short fibres in each combing head, which wouldensure a precise supervision of the combing stage itself. However, suchan arrangement would result in high investment and maintenance costs andwould cause considerable efforts in setting the various measuringdevices. In a preferred embodiment of the invention the proportion ofshort fibres is not measured or obtained for each combing head, but foreach machine, which means that only one arrangement of measuring sensorsper machine is necessary. This arrangement is connected with the processcontrol computer R2 (FIG. 6) for the area B2 of the spinning plant.Further details on measuring and obtaining the proportion of shortfibres are outlined below in greater detail. At first, however, theevaluation of the signals from the combing machines (FIG. 1) in computerR2 (FIG. 6) is explained.

It is assumed at first that a scheduled value with upper and lowertolerance limits is defined for the proportion of short fibres. As longas the signal supplied from each combing machine to the computer R2indicates that the separated proportion of short fibres is within thepredetermined tolerance range, there is no reason for computer R2 tointervene in the process with respect to the staple length. If a changein the signal from one combing machine indicates that in this machinethe proportion of separated short fibres has drifted outside of thescheduled tolerance range, a similar deviation would usually be noticedin the other machines (which process the same raw material) within apredefined time interval in the event of deficient raw material.Therefore, computer R2 should at first wait whether similar deviationsfrom the scheduled .values occur in all machines of the group. If thedeviation persists in only one machine, the error cannot be caused bydeficient raw material, but only by a malfunction in the respectivemachine or in the measuring instruments attached to said machine. Underthese circumstances computer R2 should switch off the respective machineand set a display, so that the operating personnel can eliminate thismalfunction.

If a simultaneous drift of the measured or obtained proportion of shortfibres occurs in all combing machines of the group, it is obvious thatthe error is caused by deficient raw material. Computer R2 then sends arespective signal to the process control computer R1 which isresponsible for controlling area B1. The computer R1 can then eitherinitiate a display, so that the respective new settings can be carriedout by the operating personnel, or (by making use of the various optionsfor influencing the staple length) initiate a change in the processingto bring about the desired condition in the feed of the combing roomagain. These options have been outlined in connection with the FIGS. 4and 5.

In the event of conflicting messages from various machines in thecombing room the computer R2 will come to the conclusion that there is amalfunction in the plant and therefore will raise a respective alarm.

If a control system is to be introduced, it is necessary to take intoaccount the "delay period" between the detection of an error and thearrival of the corrected material at the scanning position of thesensor. If this delay period is too long, it is recommended to refrainfrom using a control system. If, for example, the "delay period" (asseen from the respective control system) between the carding room andthe combing room is more than several hours, .it is possible that theerror in the blow room has already been "eliminated" by the completeprocessing and replacement of the deficient material when the error isdetected in the combing room. In such an event the operating personnelshould be notified of the error by an alarm, so that material that isstill "being processed" (also between the carding room and the combingroom) can be checked. This is also of importance for presentconventional spinning mills, in which delay periods between the cardingroom and the combing room can amount to several days.

With respect to the considerable delays between detecting an error inthe raw material in the combing room and the subsequent correction ofthis error in the feed material of the combing room itself, it does notmake sense to transmit continuously or quasicontinuously a deviationsignal from computer R2 to computer R1. It also does not make sense toreact to brief deviations in the results of the measuring and evaluationprocess. It is advisable to take the mean of these deviations overcertain time intervale into account in order to obtain certaintendencies. The suitable time interval has to be established on a caseto case basis. It depends both on the runtime of a lap charge 3 (FIG. 7)and the delay time within a possible control system.

Within this time interval it is possible to measure either continuously(analogue) or discontinuously. The type of evaluation can be determinedfrom case to case with respect to the results of the measuring andevaluation process, as will be outlined now in greater detail byreference to the diagrams 9A and 9B. In both diagrams the time isrepresented on the horizontal axis and the measured or evaluatedproportion of short fibres is represented on the vertical axis. Bothdiagrams are based on a predefined measuring or evaluation interval I.In FIG. 9A it is empirically established that the results of themeasurement show an irregular curve (characteristics), whereas theresults of FIG. 9B show a regular curve. In both cases a discontinuousmeasuring or evaluation method is assumed, which are represented here byfive "measuring points of time" MT within the interval I.

In a system in accordance with FIG. 9A it is hardly possible toestablish a tendency within the interval I. The results of themeasurement have to be collected for the whole interval and comparedwith the measurement results of earlier intervals by means of suitableevaluation in order to establish a tendency. The computer R2 cantherefore only determine a defect in the raw material at the veryearliest at the end of interval I and then transmit a respective signalto computer R1. In case 9B, on the other hand, it is possible toestablish the rising tendency of the proportion of short fibres evenwithin interval I, so that it is possible to intervene earlier in theprocess within a specific interval I. Computer R2 can be programmed insuch a way that it checks the supplied measurement results forpredefined tendencies (e.g. the constant rise in accordance with FIG.9B) and reacts in accordance with the results of the check. Thiscomputer, however, must in any case be programmed for the treatment ofmeasured values in accordance with FIG. 9A, as it is not possible topredict whether or not (and if yes, which) tendencies will occur.

FIG. 10 shows a diagram for explaining various options for measuring orevaluating the proportion of short fibres in the feed material of aspecific combing machine 1 (see also FIG. 7 or 8). The arrows show theflow of the material. The arrow V indicates the supply of the feedmaterial in machine 1. The arrow L shows the supply of the intermediateproduct (sliver) of the machine and the arrow A indicates the wastage(comb waste). If V, A and K are regarded as amounts of material per timeunit, the conditions can be represented by the following equations:

    V-A=L                                                      (1)

or

    A=V-L                                                      (2)

It follows that the proportion of short fibres (KFA) can be establishedby the following equation: ##EQU1##

This means that the proportion of short fibres can be determined bymeasuring A and V or by measuring V and L or by measuring A and L (inaccordance with a suitable system in accordance with FIG. 9A or 9B).Under certain circumstances it is possible to determine the proportionof short fibres sufficiently precisely by measuring the amount of combwaste A and by determining a value X, said value being an assessed valuewhich approximately represents the amount V of the feed. The value Xcan, for example, be derived from the production that is set for thecombing machine. From FIG. 10 it is clear that there are a wide numberof ways to measure or determine the proportion of short fibres. Theamount of waste A should be measured or determined in the combingmachine 1 itself. The amount V of the feed could, for example, beprovided by the preparatory stage 50 (FIG. 2). The delivery L can bedetermined in the can frame 23 (FIG. 7).

The combing machine has a clearly ascertainable influence on the staplediagram of the raw material to be spun in that this machine takes theshorter fibres out of the processing. The amount of wastage in thecombing machine clearly proves this influence, because the tomb wasteconsists nearly exclusively of short fibres (the amount of dirt in thecomb waste and the neps contained therein are negligable in thisrespect). The amount of wastage directly indicates the proportion ofshort fibres for given settings of the combing machine and for a givenarrangement of the feeding lap (lap thickness or the degree ofparallelization of the fibres). This statement applies to presentcombing machines. If in the future the percentage rate of dirt and nepsin the comb waste increases in such a way that it can no longer beneglected, it would be possible to determine fixed proportions Of thesecomponents by making samples thereof in laboratories.

The combing machine itself can be set in such a way that fibres that areshorter than a predefined length are separated, so that the followingstages need not cope with problems caused by short fibres (separatorfunction). It follows from this that after the combing room there is nomore "information" with respect to the performance of the previousstages in connection with the short fibres in the material itself. Theinformation is "erased" in the combing room.

The final results of the spinning process, however, depend on many otherfactors, in particular on maintaining the sliver count and the CV-valuesfor these slivers. Therefore it is particularly advantageous to arrangethe draw frame 11 (FIG. 7) of the combing machine as an autolevellerdraw frame. For reasons of completeness the control unit 27 for the drawframe 11 will also briefly be described hereinunder, although thisarrangement is not bindingly required for the use of the invention inconnection with the Composition of the material.

The drive of the lower roller of the roller pair 13, 15 and 17 iscarried out by the main motor M, whereby a planetary gear is arrangedin-line for the drive of the lower roller 15 and the drive of the lowerroller 13 is taken directly from the lower roller 15. A control motor M1is allocated to the planetary gear 28, whereby said motor is controlledby the control device 29. The control device 29 receives pulses from ascheduled value stage 30 in which the measured voltage initiated by themeasuring unit via the signal converter 31 and a timing signal generator32 is compared with the control voltage issued by the controlspeedometer 33 of the main motor M, which results in a scheduled voltagefor the control device.

Before entering the calender rollers 24 there is additionally provided asliver monitor for monitoring the controlled combed sliver.

If the measuring unit 12 registers a deviation from the scheduled silverthickness, the control motor M1 is activated with a delay via thecontrol unit 27, said motor engaging in the planetary gear and effectinga change in the number of rotations of the central roller 15 and thusalso the feed roller 13. The delivery roller 17, on the other hand,maintains its speed. This means that the draft is adjusted to the silverthickness determined by measuring unit 12 by means of a change in thedifference in speed between the central roller 15 and the feed roller17. In order to protect the combing machine itself from this change ofspeed in the draw frame inlet, a buffer storage means can be providedbefore the draw frame. The controlled draft zone may also be locatedbetween the pair of rollers 15 and 17. In this event the pair of rollers17 would have a variable speed. The buffer storage means would bedisposed between the draw frame outlet and the chamber press.

As will be described below, it is also possible that draw frames withother designs and with other control means are used instead of thosedescribed herein.

Another possible arrangement consists of arranging a further pair ofrollers (not shown) behind the pair of draw-off rollers 7, whereby theadditional pair of rollers is driven with a higher speed to apply aminute predraft to the sliver before it reaches the delivery table andis twisted with the other slivers.

Finally it is necessary to adjust the total production of the combingroom to the "demand" of the end spinning process. Preferably, thecontrol of the amounts is effected in such a way that the combing roomhas a certain overcapacity with respect to the production performanceand that the individual machines are operated in accordance with theso-called "stop/go" mode. In the event of higher demand by the endspinning stage the stop/go ratio is decreased and in the event ofdecreasing demand this ratio is increased. If for any reason it is notdesired to operate the combing machines in the stop/go mode, the nipnumber of the comb of the individual machines can be increased ordecreased in order to adjust the supplied amount per time unit to thedemand of the end spinning process. These settings have no influence onthe importance of the measurement or the determination of the proportionof short fibres. The measurement or determination of the proportion ofshort fibres can .be carried out and exploited irrespective of otherquality features such as the sliver count or CV. The problems concerningthe maintenance of the sliver Count or smoothing CV deviations can, forexample, be transferred to other processing stages (for example to thesecond draw passage 52, FIG. 2. The invention can therefore also berealized if the combing machines do not comprise a controlled drawframe. Such draw frames, however, are important for the invention'ssecond aspect.

Evenness and Autoleveller Draw Frames

The importance of evenness for the spinning is evident from the manual"Technology of Short Staple Spinning" as mentioned above., Presentconventional means for levelling are described in the above-mentionedbook "Drawing, Combing and Roving" or in the above-mentioned volume 3 ofthe Short Staple Series of the Textile Institute, "A Practical Guide toCombing and Roving".

Signals to be Gained from the Autoleveller Draw Frame

The sensors in the feeding or delivery section each supply a signalwhich is equivalent to the deviations in evenness of the sliver orfleece passing the respective sensor. These signals, however, cannotnecessarily be used without further treatment, as can be seen from theEuropean patent application No. 0 412 448 and U.S. Pat. No. 5,134,755the Swiss patent application No. 3100/90-4 of Sep. 26, 1991 and U.S.patent application Ser. No. 07/765,570. It is possible to generatesignals from the mentioned two signals (possibly with adjustments inaccordance with the applications mentioned above) which represent theso-called adherence to the count (longwave deviations--"drift") as wellas the V-values (shortwave deviations).

It is, however, also possible to gain the desired information from afurther signal, i.e. the so-called control signal that is used forcontrolling the controlled motor.

It has long been known to test the evenness of an intermediate productin the laboratory (off-line) by gaining respective signals and then, ifnecessary, to intervene in the process. The theory concerning the testshas been developed intensively and allows coming to conclusions on theprocessing stage which caused a predefined error. For further detailsrefer to the operating manual "Evenness test" of the Zellweger company,Uster AG, Switzerland (page 129ff).

In the course of the eighties it has become possible to obtain thenecessary signals during the operation (on-line) and to make, saidsignals available to the operating personnel through a display fordiagnosing malfunctions. This system is provided by the "SLIVER DATA"system of the Zellweger company, Uster (see the above-mentioned volume 3of the Short Staple Spinning Series). This apparatus even supplies aspectrogram of the fed and delivered material. However, it has not yetbeen proposed to evaluate the signals thus obtained through a processcontrol system and to use said signals for controlling the previousstages.

The Autolevelling Draw Frames as a Component for Determining theEvenness

The draw frame of the second passage (138, FIG. 1) is used in theconventional spinning mill as the stage that protects the end spinningstage from deviations in the evenness of the preparatory machines (blowroom, carding room and preliminary draft frame; the second passage isused as a "separator" in respect of evenness). The draw frames Of thespinning stages (flyer or end spinning machine) are not automaticallyadjustable and therefore cannot compensate errors in the feed material.

Modern draw frames of these stages are presently often provided with aregulating means and a controlling means, whereby the regulating meansis used to maintain the sliver count and the controlling means is usedto ensure the adherence to a predefined CV-value. The controllingfunction is particularly important after the combing room (due to themode of operation of the combing machine), see the books mentionedabove. As long as the draw frames of this passage fulfill the desiredfunctions, it does not make sense to investigate the performance of theprevious stages for the results in the spinning stages as the respectiveinformation is not or no longer contained in the material to be spun.

The draw frame of the second passage is mostly not the only processingstage that is provided with an evenness controlling and regulatingmeans. In principle it would be possible to provide each processingstage with an own evenness controlling means/evenness regulating means,which need not necessarily be combined with a draw frame (see, forexample, the U.S. Pat. No. 4,271,565). To equip each preparatory machinewith its own evenness regulating means would in any case be veryexpensive and, due to the high costs, is usually not taken into account.Even if this expensive arrangement is realized under certaincircumstances, it is possible to determine the last stage before thespinning as the control unit in the sense that the results of theprevious stages are checked here through the process control system and,if necessary, measures are undertaken in said previous stages.

Even if, however, more than one stage is provided with an evennesscontrol or regulating means, the control or regulation of the stagedisposed in front of the separator will be less efficient than thecontrol or regulation of the separator itself, because repeatedinterventions in the feed material usually do not lead to an improvementin the quality of the material, but to a deterioration in the quality.Therefore it applies, also for technical reasons, that suchinterventions should be provided at the fewest possible positions, atleast with respect to shortwave deviations in the evenness. With respectto longwave deviations, however, it can be preferable to provide thesuitable control or regulating means in stages situated immediately infront, in particular in front of the carding machine.

An autoleveller draw frame for compensating shortwave deviations in thematerial is necessary after the combing stage in order to compensate thepiecing to the utmost extent. As was already shown in connection withthe composition of the material, it is possible to integrate a "drawingpassage" arranged behind the combing in the combing machine itself, i.e.the combing machine can serve as a "separator" both for the proportionof short fibres as well as for the "preparatory evenness". The term"preparatory evenness" in this context means the evenness of the feedmaterial that is supplied to the spinning stage and that cannot beimproved any more with respect to its evenness.

As was already shown in connection with the composition of the material,an increased wastage of short fibres causes a loss in material, whichmeans a respective change in the evenness that is noticeable in theautoleveller draw frame arranged behind the combing machine, i.e.additional regulating work is necessary to supply a sliver with apredetermined count to the spinning stage.

If an autoleveller draw frame is built into the combing machine itself,it is possible that a correlation between the regulating work and theseparating work in the machine control unit can take place, whereby saidmachine control unit receives both the comber waste measuring signalsand evenness value signals. If the combing machine is not provided withan autoleveller draw frame, a process control computer can carry out therequired correlation if the necessary output signals of the two processstages are supplied to it.

This correlation helps to avoid erroneous conclusions, which couldotherwise arise because the essential tasks of the combing machine(namely, the separation of short fibres) lead to a change in anotherquality (the evenness). This change in evenness must not be regarded as"erroneous behaviour" in the preparation with respect to the evenness,but must be evaluated (like an increase in the amount of the combedwaste) as the symptom of a defect in the material or in the processingof the material.

Interventions by the Control or Regulating Unit

Tolerance limits for the material supplied to the separator can now bedetermined in the process control computer, so that no interventions aremade as long as the deviations in the evenness of the incoming materialare within these tolerance limits. The tolerance values can be adjustedto the performance of the separator in such a way that, for example, ifa deterioration of the incoming material is noticed, an intervention isnot carried out as long as the separator is able to cope with thedeviations in evenness with a minimum safety margin. An interventionbecomes necessary if it is noticed that the deterioration has reachedthe safety margin. It is also possible to evaluate tendenciesbeforehand, as was described in connection with the composition of thematerial, so that an intervention can be carried out earlier if it isnoticed that a continuous deterioration has begun, becausedeteriorations and improvements should approximately balance one anotherover the time in normal operating conditions.

However, the system can also be used to "optimize" the line in the sensethat a deterioration of the quality of the previous stages is initiatedif the separator still has unused reserves. As the quality is usuallyachieved at the expense of the production, such a procedure can lead toa more efficient exploitation of the interactions between the processingstages with respect to production and quality. The same applies to theselection of the raw materials. By mutually adjusting the production inthe various stages by means of the process control computer it ispossible to empirically determine the optimal settings for moresensitive materials or the effects on cheaper materials.

The spectrogram is of the utmost importance for the evaluation of theevenness test. Only this analyzing means enables the identification ofthe error source (see the above-mentioned manual of the Zellweger AG,Uster). In the preferred embodiment of this invention the evennesssignals of the Separator are obtained in such a way that they allow theSpectrum analysis.

The spectrum analysis, however, allows at best the identification of theprocessing stage that has caused a particular error. The identificationof a certain machine as the source of the error requires tracing theflow of the material. Systems for tracing the flow of the material areknown, but they are very expensive. In order to limit the length of thisdescription, the tracing of the material flow Will not be treated assuch in this application. The combination of the present invention withtracing the flow of the material in the process control system is,however, the preferred embodiment and a material flow tracing systemsuitable for this purpose is described in the above-mentioned Germanpatent application No. 40 24 307 and in U.S. patent application Ser. No.07/852,153. The statements contained in said application are herebyincluded in the present description by this reference.

Tracing the flow of the material is based on simulating the flow of thematerial in a computer or a computer system (with a plurality ofcomputers connected to each other. For this simulation "material units"are defined which can be recorded in the plant by means of the sensors.The plant is provided with such an arrangement of sensors that

(1) the paths of the material through the plant are divided intoSections between the sensors, whereby the allocation of a material unitto a section represents a locating precision that is sufficient fortracing the material flow and

(2) the sequence of the movement of the material units past the sensorsallows the definite identification of the units (without having to markthe units).

The sensors are connected with a computer (system) in such a way thatthe movement of a material unit past a sensor is registered by thecomputer (system) and allocated to a time coordinate. The material unitstherefore are provided with both location and time coordinates which arestored in the computer for such a period as to allow the determinationof the flow of the material at a later time, i.e. at least up to thepoint of time at which said material units leave the plant.

Preferred Embodiments of the Autoleveller Draw Frame

The second aspect of the invention relates to the application ofautoleveller draw frames, i.e. draw frames in which the draft can becontrolled or regulated in order to balance deviations in the materialof a supplied fibre structure. Such draw frames are often used inso-called autolevellers in short-fibre spinning mills. They can,however, also be used in carding machines, combing machines and combingpreparatory machines in short-fibre spinning. The same principles arenaturally suitable for the use in long-staple spinning mills.

The principles of control engineering have been applied for severaldecades in autoleveller draw frames. They have enabled the continuousimprovement of the quality of the fibre structures to be processed (tothe extent that this quality was only defined by the evenness of themass per unit of length).

In the same period of time intensive efforts have been made to gain aclear definition of the term "quality" with respect to the evenness ofthe fibre structure. These efforts have led to generally acceptedtesting methods with the subsequent availability of suitable testingdevices.

By means of the presently applied technology in combination with aquality-oriented organization of the spinning mill nearly every spinningmill is in a position to avoid or correct most of the (relatively major)defects and to produce fibre structures of good average quality.

Due to continuously rising demands in the quality it is now necessary tofurther raise the already good quality level. Thus, technical areas arereached in which it is no longer sufficient to apply the basicprinciples of control engineering or the basic principles of statisticalquality control in the spinning mill. In order to achieve a furthersubstantial improvement the quality it is now necessary to take a closerlook at the more intimate interactions between the applied measuringprinciples, control principles, drive systems, drafting forces andmaterial qualities. In this respect it is necessary to bear in mind theprinciples of the evenness test for sliver structures, which havealready been determined by standards.

The quality control in the spinning mill is presently mostly carried outin the laboratory ("off-line"). For this purpose samples are collectedfrom the processing line, carried to the lab and tested. The testresults are to provide conclusions on the settings of the machines or toallow making adjustments to the material to be processed in order tofulfill the quality requirements of the desired final product. Theleading manufacturer of testing equipment is Zellweger G, Uster,Switzerland. The user manual of this company titled "Evenness Test"comprises approx. 230 pages and describes at least six different testcriteria which supply various information about, evaluating the evennessof a fibre structure (i.e. the diagram, the imperfections or raredefects, the spectrogram, the mean factor and the length variationcurve).

There is enough time in the laboratory (off-line method) to analyze theinformation, to come to a suitable interpretation of the various resultsand to the respective conclusions. If, however, such methods are appliedin normal operation "on-line", whereby it is intended to intervene inthe process based on measured values that were just obtained, it ishardly surprising that there is a high risk of erroneous conclusions.

The previously mentioned proposals for a more precise examination ofproducts in the operation ("on-line") are not aimed at allowinginterventions in the processing, but at initiating an alarm, atcollecting operational data or analyzing a process (e.g. U.S. Pat. No.4,758,968), so that a closer examination can be carried out by thepersonnel or that the staff can carry out purposive support work. Asystem in accordance with the DE-PS 32 37 371 and GB 2,132,382 belongsto this category. According to these disclosures a yarn produced inaccordance with a jet-spinning process is tested both with respect tothe spectrogram and the Uster value (unevenness coefficient). Thisallows identifying errors in the drafting device of the jet-spinningmachine itself, which can lead to an exchange of the deficient parts.This method, however, does not allow conclusions on the performance ofthe preparatory stages.

A proposal for monitoring a draw frame was made in EP 340 756. Inaccordance with a first variation of this proposal limit values are tobe determined for a signal supplied by the outlet measuring unit,whereby an alarm can be raised or the machine turned off if a limitvalue is exceeded. In this case the product (the supplied silver) shouldbe checked by the staff. The results of this check are to provideconclusions on measuring or controlling errors.

A second variation of the same proposal provides the determination oflimit values for the control signal that defines the draft, wherebyhere, too, an alarm is raised or the machine is turned off if a limitvalue is exceeded. In this case the feed sliver should be checked by thestaff. The results of the check are to provide conclusions on errors inthe inlet measuring system or the production of the feed material (i.e.in the production machines before the draw frame).

The monitoring of the measuring signal from the outlet measuring systemcan provide some information on malfunctions. However, this measurealone is not sufficient to achieve a substantial improvement in thequality. The monitoring of the control signal in combination with analarm or turning off the machine as was proposed in EP 340 756 hardlygives an advantage. By the time the staff carries out the check, thedefective feed fibre structure has long been processed (corrected) bythe draw frame, so that important information with respect to the erroris no longer available. Because the supervision is set only to react toa short-term (possibly rare) "freak value", the segment of the feedfibre structure that is examined by the staff does not contain anyinformation on the "event", so that again there is the risk of coming toan erroneous conclusion. The examination does not take place during theoperation, but "off-line".

It is the object of the invention in a third aspect to further developthe autoleveller draw frame in such a way that the interactions that aredecisive for its function are taken into account better than in thepast.

The invention (in the third aspect) provides an autoleveller draw framefor fibre structures which comprises at least one draw zone, a drivesystem that can be controlled or regulated for determining the draftheight in the mentioned draw zone, a programmable control unit for saiddrive system and at least one sensor for determining the fibre mass perunit of length that passes a measuring position. The draw frame ischaracterized in that a signal determining the draft is stored over apredefined period of time. From said stored values information is gainedfor adjusting the draw frame and/or evaluating the quality of the fedfibre structures. The above information comprises, for example, theCV-value of the fed fibre structure, the spectrogram of the fed fibrestructure, and/or the length variation curve of the fed fibre structure.The control unit preferably comprises a digital signal processor, forexample Motorola's 56001.

The signal that defines the draft can be the output signal of a sensoror the control signal for the drive system. A signal "that defines thedraft" within the scope of this invention means that it has a direct orindirect influence on the draft, even if other signals also have such aninfluence.

The information can be gained by the control unit mentioned above and/orby a process control system, whereby in the latest case the storedvalues are preferable transmitted to the process control system via thecontrol unit, e.g. in accordance with our Swiss patent application No.1025/91-2 of Apr. 5, 1991 and U.S. application Ser. No. 07/927,307. Thegaining of such information by the control unit itself is only possiblein the event that said control unit comprises a digital signal processoror a device with similar or better processing power.

The sensor is preferably suited to trace shortwave deviations in themass. In order to process such signals in accordance with digitaltechnology it is necessary to digitize them, which is carried out byperiodic scanning. In accordance with a preferred embodiment of thecontrol unit the scanning rate is selected higher than 2000 Hz,preferably in the range of 2500 to 3500 Hz. Such a sigma can beprocessed in the processor in accordance With the fast. Fouriertransformation method to allow the spectrum analysis.

The scanning rate of the control unit preferably remains constant. Thespeed of the passing material, however, is changeable. The control unitis also preferably provided with a sensor which reacts to the entrancespeed of the material, so that the control unit (despite the constantscanning rate) is able to carry out a corrective action per incomingunit of length. The respective storage means are provided.

This preferred embodiment givers the advantage that the information canbe gained from signals which are also used for controlling thecorrective actions, thus increasing the uniformity of the informationcontent of the various signals.

Based on the same or similar considerations, the operator support thatis provided by the signals according to this invention is providedthrough the user interfaces (operator console or indicator boards) ofthe affected machines, as is described in the above-mentioned PCT patentapplication PCT/CH 91/0097 and U.S. patent application Ser. No.07/798,813. In order to abridge the length of this description, theoperator support shall not be treated herein as such. The statements ofthe PCT 91/0097 are, however, included in the present Specification bythis reference.

FIG. 11 shows a schematic display of an embodiment of the draw frame inaccordance with our European patent application No. 0 411 379 and U.S.Pat. No. 5,248,925.

In the system in accordance with FIG. 11 several slivers 215.1-215-6, atotal of six in the example, are combined to form a loose fleece andguided through several roller systems 201-206. Because thecircumferential speed of the rollers increases in two steps in theconveying direction of the fibre material, said fibre material ispredrawn (preliminary draft) through the first stage and further drawnthrough the second stage until it reaches the desired cross section(main draft).

The fleece leaving the draw frame is thinner than the fleece of the fedslivers 215.1-215.6 and respectively longer. As the drafting processescan be controlled depending on the cross section of the slivers fed, theslivers or the fleece is evened out during its passage through the drawframes, i.e. the cross section of the outgoing fleece is more even thanthe cross section of the fed fleece or the slivers. The present drawframe comprises a preliminary draw zone 211 and a main draw zone 212.

The slivers 215.1-215.6 are supplied to the draw frame through twosystems of conveying rollers 201 and 202. A first system 201 consists,for example, of two rollers 201.1 and 201.2 between which the conveyanceof the Slivers 215.1-215.6 that are fed and combined to form a loosefleece takes place. In the conveying direction of the slivers a rollersystem 202 follows which consists here of an active conveying roller202.1 and two passive conveying rollers 202.2, 202.3. During the feed bythe roller systems 201 and 202 the fed slivers 215.1-215.6 are broughttogether next to one another in order to form a fleece 216. Thecircumferential speeds v₁ and v₂ (=v_(in)) of all rollers of the tworoller systems 201 and 202 of the feed are equivalent, so that thethickness of the fleece 216 is essentially equivalent to the thicknessof the fed slivers 215.1-215.6.

After the two roller systems 201 and 202 of the feed a third system 203of predrawing rollers 203.1 and 203.2 follows in the conveying directionof the fleece whereby the fleece is further conveyed by means of saidthird system. The circumferential speed v₃ of the predrawing rollers ishigher than the speed of the conveying rollers v₁,2, so that the fleece216 is drawn in the preliminary draw zone 211 between the conveyingrollers 202 and the predrawing rollers 203, whereby its cross section isreduced. Simultaneously, a predrawn fleece 217 comes about from theloose fleece 216 of the fed slivers. Following the predrawing rollers203 there is a further system 204 consisting of an active conveyingroller 204.1 and two passive conveying rollers 204.2, 204.3 for furtherconveying the fleece. The circumferential speed v₄ of the conveyingrollers 204 is the same as v₃ of the predrawing rollers 203.

Following the roller system 204 for the further conveyance in theconveying direction of the fleece 217 there is a fifth system 205 ofmain distorting rollers 205.1 and 205.2. The main distorting rollershave a higher surface speed v₅ than the previous conveying rollers, sothat the predrawn fleece 217 between the conveying rollers 204 and themain distorting rollers 205 is drawn to the finally drawn fleece in themain draw zone 212, whereby the fleece is parallelized through a funnelT to a sliver.

The finally drawn silver is led away from the draw frame between a pair206 of delivery rollers 206.1, 206.2 whose circumferential speed v₆(=v_(out)) is equivalent to the speed of the previous main distortingrollers (v₅) and deposited, for example, in rotating cans 213.

The roller systems 201.2 and 204 are driven by a first servomotor 207.1,preferably through a toothed belt. The predrawing rollers 203 aremechanically coupled with the roller system 204, whereby thetransmission can be adjustable or a scheduled value can be set. The gear(not shown in the Fig.) determines the ratio of the circumferentialspeeds of the feed rollers (v_(in)) and the circumferential speed v₃ ofthe predrawing rollers 203.1, 203.2, i.e. the predrafting ratio.

The roller systems 205 and 206 are driven by a servomotor 207.2. Thefeed rollers 201.1, 201.2 can also be driven by the first servomotor207.1 or, optionally, by an independent motor 207.3. The two servomotors207.1 and 207.2 each comprise its own controller 208.1 or 208.2. Thecontrol for each of them is carried out through a closed control loop208.a, 208.b or 208.c, 208.d. In addition, the actual value of the oneservomotor can be transmitted to the other servomotor in one or bothdirections through a control link 208.e, so that each of them can reactpertinently to deviations of the other.

At the entrance to the draw frame the mass or a value proportional tothe mass, e.g. the cross section of the fed slivers 215.1-215.6, ismeasured by a measuring instrument 209.1. At the exit from the drawframe the cross section of the outgoing Sliver 216 is measured by ameasuring instrument 209.2.

A central processing unit 210 transmits an initial setting of thescheduled value for the first drive via 210.a to the first controller208.1. During the drawing process the measured values of the twomeasuring instruments 209.1, 209.2 are continuously transmitted via thelinks 209.a and 209.b to the central processing unit. From thesemeasured values and from the scheduled value for the cross section ofthe outgoing sliver 218 the scheduled value for the servomotor 208.2 isdetermined in the central processing unit or any other existingelements. This scheduled value is permanently transmitted to the secondcontroller 208.2 via 210.b. By means of this control system (the "maincontrol system") it is possible to compensate deviations in the crosssection of the fed slivers 215.1-215.6 by the respective control of themain drafting process and to thus achieve the evening out of the sliver.

The draw frame shown in FIG. 1 is designed for a drafting device, but itcan also be built into a combing machine, whereby the feed cans can bedropped in this case (as is shown in FIG. 7).

The lower part of FIG. 11 shows the adjustment of this system to theinvention in this third aspect. In a first embodiment a memory 210 isallocated to the central control unit 220 of the machine, said memorybeing used to store the signals or certain signals of the draw framecontrol system for evaluation. If the processing speed of the centralprocessor in the control unit 10 is high enough, it is possible toselect such a high scanning rate that a spectrogram of the input signal(from sensor 209.1), the output signal (from sensor 209.2) and/or thecontrol signals (signals transmitted to the motors 207.1 and/or 207.2)can be obtained.

A draw frame control unit in accordance with FIG. 11 is usually designedto carry out control actions in the material (changes in processing thematerial) not continuously, but after a certain interval. The durationof this interval is preferably selected not constant, but is adjusted tothe feed speed in such a manner that the actions are each carried out atthe end of a predefined length of fleece. In this respect it is possibleto complement the shown arrangement in such way that the feed speed at,for example, the roller group 202 is determined and used for controllingthe actions aimed at intervening in, the processing. In this event it isnecessary to provide storage means (not shown) in the draw frame controlunit to store the control signals and to activate them at the righttime.

The evaluation of the values contained in the memory 220 does not takeplace depending on the feed speed, but in accordance with the time. Whena spectrum analysis is made, the time functions are transformed tofrequency functions by means of the fast Fourier transformation method.The time necessary for the transformation depends on the processingspeed of the processor and the number of frequencies (or frequencyranges) that have to be examined separately. Preferably at least 1024separate frequency ranges have to be examined for achieving asatisfactory analysis of a feed material.

Such an evaluation, however, requires considerable processing andstorage capacities in the machine itself. This may often not be thecase, so that the analysis has to be transferred to the process controlcomputer PLC. For this purpose a databus DB may be provided and thecontrol unit 10 can be provided with an interface SNM to said databus,whereby the computer PLR also comprises an interface SNR to the databus.

Neither the processing speed nor the storage capacity will usually limitthe desired analysis in process control computer. In this case, however,the prerequisite for the analysis Consists of the fact that the processcontrol computer must have access to the "raw data" of the respectivesensors, as is shown, for example, in the above-mentioned Swiss patentapplications No. 189/91 and 1025/91. The statements made in these twospecifications are hereby included in the present description by thisreference. Reference is also made to U.S. patent application Ser. No.07/927,307.

The above-mentioned "raw data" are not to be understood as the actualoutput signals of the respective sensors. These signals may be preparedby the machine control unit (at least for the transmission to theprocess control computer). It is important that the essentialinformation content is maintained for the intended analysis.

The Term Separator

The term "separator" has been used in some places in this description.This term is not common in the field of spinning engineering and willtherefore briefly be outlined below.

The "separator" is the last position in a spinning line which carriesout certain changes in the material to be processed (e.g. it changes thecomposition of the material, separates short fibres and/or changes theform of the structure). This position causes certain changes (ifnecessary), i.e. the position is not only a measuring position. Theeffect of a separator (its success) can be measured and the measuredresults are a measure for the (a defined) performance of the previous(i.e. those situated immediately beforehand) processing stages. Theseparator can therefore serve as a control station. Finally, insofar asthe separator carries out the changes provided by it, it "erases" therespective information in the processed material, so that after thematerial has passed the separator there is no (more) information on theperformance of the previous stages.

We claim:
 1. An autoleveller draw frame for fibre structures, said drawframe being arranged after a plurality of successive textile machines ina fibre processing plant, for processing said fibre structures, saiddraw frame comprising:at least one draw zone; a controllable drivesystem for defining draft height of the fibre structures in said drawzone; a programmable control unit for controlling the drive system; atleast one sensor for determining mass per unit of length of the fibrestructures passing a measuring position; means for storing a signaldefining the drafted fibre structures for a predetermined period oftime, said signal being representative of information for affecting aquality parameter of the fibre structures; said means for storing saidsignal including a memory unit for storing said signal; and a processcontrol computer, said process control computer also being utilized forrecalling said signal stored in said memory unit for use in controllinga quality parameter of the fibre structures in said plurality ofsuccessive textile machines of said fibre processing plant.
 2. Anautoleveller draw frame in accordance with claim 1, wherein:said signalis representative of information for adjusting the draw frame.
 3. Anautoleveller draw frame in accordance with claim 1, wherein:said signalis representative of information for determining a value of the qualityparameter of the fibre structures.
 4. An autoleveller draw frame inaccordance with claim 1, wherein:said signal is representative ofinformation for determining a value of the quality parameter of thefibre structures and is representative of information for adjusting thedraw frame.
 5. A method of using the autoleveller draw frame inaccordance with claim 1, said method comprising:obtaining a signaldefining the drafted fibre structures and storing said signal for apredeterminate period of time.
 6. A method of using the autolevellerdraw frame in accordance with claim 5, wherein:said obtaining a signaland storing said signal comprises obtaining a control signal of saidprogrammable control unit and storing said control signal forevaluation.
 7. A method of using the autoleveller draw frame inaccordance with claim 5, further comprising:adjusting the draw frame inresponse to said signal after elapse of said predeterminate period oftime.